Rackspace operates two cloud infrastructures, a legacy Slicehost system and a next-generation OpenStack system. For reasons Toman explains to ServerWatch in an exclusive interview, Rackspace is using Xen server virtualization technology for both systems.

Until this week, the open source Xen hypervisor had been developed under the auspices of Citrix, a vendor that Rackspace both partners with and competes against. Xen is now migrating to the Linux Foundation where it will be developed in as a collaborative project.

OpenStack, which was initially created by Rackspace along with NASA, can run any number of hypervisors, although the open source KVM hypervisor might well enjoy a technological advantage.

"Our decision to use Xen in OpenStack was largely due to the fact that we already had several thousand nodes deployed in Xen in another environment and we wanted to make the transition easy," Toman said. "We also have a lot of operational knowledge managing large scale deployments of Xen hypervisors."

For Rackspace, the KVM hypervisor would have represented a change and was not seen as the best place to invest resources.

The original decision by Rackspace to use Xen was made around 2008. At that time, Xen was seen as being more stable than KVM. Additionally, Citrix has a relationship with Microsoft, which meant that Rackspace could get a higher level of Windows support.

Xen Collaboration Project

Rackspace is not part of the Steering Committee at the Linux Foundation that will now help to oversee Xen development, but Toman did state Rackspace has been in discussion with Citrix to become more active in that effort as it moves forward.

Xen's move to the Linux Foundation overall is seen as a very positive one from Rackspace's standpoint. Toman commented that since Xen had been run by Citrix, there was a notion that perhaps it was a bit more proprietary than KVM.

"I think this is a good move by Citrix -- that Xen is going to the Linux Foundation -- it's absolutely open source and they don't have some secret plan to make it a fully proprietary offering at some point," Toman said.

He stressed that Rackspace did not have this concern because of its relationship with Citrix.

"We're ecstatic about the move and the future of Xen and what it represents," Toman said.

CloudStack

In 2012, Citrix walked away from OpenStack, opting to push its own CloudStack technology, which is being developed as an Apache Software Foundation effort.

"I think that probably everybody in the OpenStack community would just as soon hope that CloudStack never happened," Toman said. "I think it adds some confusion to the marketplace."

Toman admitted there was some angst when CloudStack was created; however, he understands Citrix's motivation in trying to build their business.

"I think the market will bear out whether in the long run it becomes successful or not," Toman said.

Watch the video interview with Troy Toman below:

Sean Michael Kerner is a senior editor at ServerWatch and InternetNews.com, the news service of the IT Business Edge Network, the network for technology professionals. Follow him on Twitter @TechJournalist.